To make delicious coffee, it must be fresh! Old coffee has a flat, expressionless taste with an unpleasant bitterness. It is because, upon contact with air, coffee quickly exhales and ages. This article explains why and what to do about it.

Many chemical changes take place in coffee during roasting. The most important of these are: reducing the amount of water from 11% to 3%, Maillard reaction, and caramelization. Besides, during the frying, essential oils are released, dozens of substances are released and concentrated. We will explain what happens in beans during and after roasting and why it is significant to drink freshly roasted coffee.


What Happens to Coffee During Roasting


There are three main stages: 

  • drying, in which excess moisture evaporates 
  • at about 212 ° F, the Maillard reaction begins, during which enzyme notes are forming - floral, fruit, and berry 
  • from 338 ° F, caramelization begins, during which typical aromas are setting up: chocolate, nuts, spices, and caramel.


The Maillard reaction is one of the main processes for color, taste, and aroma. During it, amino acids begin to interact with sugar, and as a result, hundreds of aromatic compounds are forming. The most important ones are:


  • furans, which give the coffee a sweet caramel flavor;


  • pyrazines, which are responsible for the floral notes in the taste;


  • ketones, which are responsible for the oily taste;


  • caffeol gives the coffee its characteristic smell.


Due to the Maillard reaction, coffee beans turn brown, essential oils are released, fiber is destroying, and the glucose content decreases.


Plus, moisture evaporates from the grains. In the article about hulling, we wrote about the moisture content of green grain should be 10–12%. During roasting, it is reducing to 3%. Since moisture leaves, the grain becomes porous and light.


There is an opinion that the darker roast has less caffeine in the coffee. But when roasting, the caffeine does not burn. The total weight of the grain decreases but the concentration of caffeine, on the contrary, increases.


What Happens to Coffee After Roasting


After roasting, carbon dioxide begins to evolve inside the grain. In some industries, the beans are not packaging immediately after roasting. Coffee beans allowing to rest. That excess gas is released. But there is a good reason not to. It is a reason to drink only freshly roasted coffee.


This reason is the environment. Roasted coffee is highly hygroscopic. It means that it quickly absorbs and releases moisture. At once, it very quickly takes in foreign odors. Upon contact with oxygen, it begins to oxidize and lose essential oils. Essential oils are responsible for the richness of taste and aroma.


In simple terms, on contact with oxygen, coffee starts to run out of steam and does it quite quickly. As a result, it turns out that the coffee needs to release carbon dioxide, but it cannot be in contact with oxygen. If you let it rest after roasting, some of the gas will come out, but the coffee will lose its richness, although it will not become awful. And if you immediately close it in a package, it will swell and easily burst, which again will lead to contact with air.

The degassing valve allows the gas to escape., but the coffee didn't contact air. Packages with this valve prevent coffee from drying out too quickly. 


How long does coffee last and why


Coffee reaches its peak flavor on the fourth to the seventh day. If the coffee is storing in a closed container with a degassing valve, the taste peculiarities persist for a month or two. After a couple of months, the taste becomes flat and unpleasant bitterness appears. Ground coffee in an open pack lasts a week. The ground coffee fizzles out in hours.


You can tell fresh from stale coffee by smell. Fresh coffee smells very bright - even not very dedicated people immediately feel it. If the coffee is light to medium roasted, it should be free of oil stains. In a dark roast, oil appears on the surface already during roasting.


If buying ground coffee at the supermarket, there is no chance that it will be truly delicious. Firstly, there are no degassing valves on the packages; secondly, due to the peculiarities of logistics, the coffee was roasted and ground two months ago, or even earlier; thirdly, the quality of the grain probably was a sleaze.


In some specialty stores, coffee is placed in clear plastic containers and then packaged by weight. This storage method is also not suitable. The plastic containers are leaky and coffee is exposing to light. The roasting date is most likely a secret even for sellers.


Ideally, coffee should be packed in an opaque container with a degassing valve. The date of the roast must be indicated on the packaging. If the coffee is more than a month old, we recommend looking for something fresher, and after opening the package - drink it in one or two weeks, no more.


What to remember


  • Better to buy coffee that is roasting in the US. Foreign coffee, when imported, loses time on the road. It cannot be fresh.


  • The packaging must be opaque with a degassing valve. It is necessary.


  • It is best if 3 to 14 days have passed since the roasting date. The coffee will be at its peak. You still have time to drink it fresh. It's normal if the coffee roasted three weeks or a month ago. In this case, it is better don't buy a lot. Do not take coffee after roast one and a half to two months.


  • Fresh ground coffee is worth buying if you plan on drinking it several days in advance. You should not take stale ground coffee. 


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